code: def test_accept_empty():
      """Tests an empty dataframe is returned if you give an empty dataframe"""
      empty_frame = pd.DataFrame()
      result = regret(empty_frame)
  
      assert result.empty
      assert result.equals(empty_frame)
  
      empty_frame = pd.DataFrame(columns=["id", "objective"])
      result = regret(empty_frame)
  
      assert result.empty
      assert "best" not in result.columns
      assert "best_id" not in result.columns
      assert result.equals(empty_frame)
  
file_path: orion/tests/unittests/analysis/test_regret.py
imports: import pandas
  import pytest
  from orion.analysis import regret
label_desc: Use image node_id 2 for calling a global function with example usage: test_accept_empty() without return types